1. Field of the Invention
The present invention relates to a detection method and, more particularly, to a detection method for detecting a detection target formed of a plurality of regions from an image.
2. Description of the Related Art
In the field of monitoring cameras or the like, there are known methods for detecting a human body from a photographed image. As conventional human body detection methods, there are known “an intruder identification system” described in Reference 1: Japanese Laid-Open Patent Publication No. 6-20049 and “a composite type monitoring device” described in Reference 2: Japanese Laid-Open Patent Publication No. 2000-331252.
These are methods for detecting a moving object by using frame difference or the like to a picture or detecting a person by using a different sensor such as an infrared camera or the like.
On the other hand, in relation to methods in the field of human engineering such as man-machine interfaces and the like and the field of computer graphics or CG such as VR (virtual reality), animation and the like, a study of reproducing the attitude and operation of a person using a strict human body model has been performed.
For example, according to Reference 5: “Keyframe Tracking of Human Body in 3D Motion from a Monocular Image Sequence”, a technical report of The Institute of Electronics, Information and Communication Engineers Vol. J81-D-II, No. 9, 1998, pp. 2008-2018, a method for applying a three-dimensional human body model to a person in an image is used. Reference 5 proposes setting a key frame to prevent an increase in application error and constraining the position and attitude of the model.
Further, in the authentication field, a method for specifying a facial region using standard positional relationship among such regions as an eye (eyes) and a mouth in face authentication is described in Reference 3: Japanese Laid-Open Patent Publication No. 7-311833 entitled “Human Face Detecting Device”.
Moreover, a technique for specifying a head region using the standard positional relationship among regions to detect a head and obtaining the number of passengers waiting for an elevator is described in Reference 4: Japanese Laid-Open Patent Publication No. 8-127476. In Reference 4, the certainty factors of a hair region and a face region and the height relationship among regions are used to calculate the certainty factor of the head.
However, the methods described in both References 1 and 2 have a disadvantage of being incapable of performing high-level processing such as the measurement of number of persons, the estimation of the attitude of a person and the recognition of operation.
The method described in Reference 5 has a disadvantage in that collation using the key frame such as the setting of an initial value should be performed manually. The method described in Reference 5 has also a disadvantage of heavy calculation load since many attitude parameters are set for the three-dimensional model.
The technique of Reference 3 has a disadvantage of being incapable of detecting the face region if an eye or eyes cannot be detected because illumination conditions change or a target person wears sunglasses or the like (partial regions disappear due to occlusion).
The technique of Reference 4 is limited to the detection of the head and is disadvantageously incapable of being applied to a human body the attitude of which freely changes.